1. Field of the Invention
The present invention relates to a method for producing a needle diamond-type structure.
2. Description of the Related Art
Needle diamond-type structures, especially those which have been subjected to doping to attain electrical conductivity are used in electron-emitting sources for display, gas sensors, electrode materials and the like. To be used for such purposes, it is generally important for the needle diamond-type structure to have a minute and regular structure in order to improve the performance of the end-product. A conventional method of forming such a minute and regular structure involves steps in which a mask having a etching-resistant property is applied on a diamond substrate; patterning is performed using a photomask; and then selective etching is performed using a dry etching method.
In addition to the above conventional method, a method for producing a regularly-arranged, minute needle-type structure is also known, in which a casting-structure having minute and regularly arranged dents (cavities) is made of materials like Si in advance using conventional lithography; a diamond is grown by a vapor growth method while using the casting-structure as a mold; and then the casting structure used as a mold is selectively removed by dissolving.
However, the conventional methods employing a resist and exposure technique are limited with regard to minuteness of structures that can be fabricated, due to the diffraction limit of light. Further, if electric beam depiction is used, which can draw more minute patterns, drawing of a pattern requires a longer time, thereby causing a significant increase in the total cost. Moreover, all conventional patterning methods wherein a resist is used commonly require rather complicated steps of application of a resist, exposure to light, and removal of the resist.
With respect to the other type of conventional method, in which a casting structure is made using conventional lithography and a diamond film is formed thereon by a vapor growth method, the limit of fineness depends on the uniformity of the vapor-grown diamond film. Accordingly, since nucleation density of diamond in a vapor growth method is low, there is a certain limit to the fineness of processing.